Anchors for concentric coil springs



' April 26, 1960 w. P. KIMSEY ETAL 2,934,336

ANCHORS FOR CONCENTRIC COIL SPRINGS Filed Aug. 23. 1957 INVENTORS womoyfi kmszy By WILLIAM. Lyomsmom 7-7 TOR 5Y5 United States Patent ANCHORS FOR CONCENTRIC COIL SPRINGS Woodrow P. Kimsey, Lockport, and William L. Holmstrom, Joliet, Ill., assignors to Caterpillar Tractor Co., Peoria, Ill., a corporation of California Application August 23, 1957, Serial No. 679,864

1 Claim. (Cl. 267-61) This invention relates generally to anchors for coil springs and particularly to improvedmeans for anchoring a plurality of concentrically disposed tension springs. The present invention is primarily intended for apparatus requiring the use of more than one tension spring where, because of space limitations, insuflicient force is available from a single spring for efficient performance.

One of the advantages of the present invention is that the force of a coil spring may be augmented substantially by the incorporation of one or more other springs disposed within said spring which, through the use of the anchoring arrangement of the present invention, causes all the springs to be stressed simultaneously, thereby multiplying the spring force available.

It is, therefore, the principal object of this invention to augment the force of a spring confined within a limited space by interposing one or more springs within the confines of said first spring, and cause them to be stressed simultaneously by the use of anchoring means connected individually to each spring.

Another object of this invention is to provide an arrangement of multiple concentric springs wherein spring damage caused by interference between the respective springs is minimized.

. Further and more specific objects and advantages of this invention are made apparent in the following specification, wherein a preferred form of the invention is described in detail by reference to the accompanying drawings.

In the drawings:

Fig. l is a view illustrating the anchor arrangement of the present invention in assembly with one end of a pack of two concentric tension springs with parts broken away to show the details of assembly;

Fig. 2 is a sectional view of the anchor at the other end of the spring illustrated in the condition obtaining prior to installing the spring adapter to the outermost spring; and

Fig. 3 is a view taken along the line III-III of Fig. 2 showing the method by which a loop is secured to the innermost adapter of the anchor.

Referring to Fig. 1, one end of a spring pack is shown as comprising two tension springs 11 and 12, which are illustrated in the condition of assembly with a spring anchor generally designated 15. Anchor 15 comprises an adapter 16 having a helical recess 17 for threadably engaging the inner surface of the outer spring 11. Anchor 15 further comprises at least one other adapter 18, likewise provided with a helical recess herein designated 19, for threadably engaging the inner portion of the inner spring 12. While a spring pack consisting of two springs is illustrated in the drawing it is to be understood that additional springs may be employed through the use of additional adapters similar to but larger than the adapter 16.

Adapter 18 is formed with .a reduced diameter portion 2,934,336 Patented Apr. 26, 1960 Ice A 21 extending axially inwardly of the innermost spring 12. Suitable diametrically opposed slots 22 and 23 (see also Fig. 3) extend throughout the length of adapter 18 to receive a loop member 24. The loop member 24 is first formed in the shape of a U, the legs of which are threaded through slots 22 and 23 until the ends 26 and 27 thereof extend beyond the opposite face 28 of adapter 18. At this point loop ends 26 and 27 are bent to lie adjacent each other as shown in Figs. 2 and 3 and the assembly is completed by tack-welding the loop ends together as indicated at 29. To assist in forming the loop ends, the end portions of the slots 22 and 23 may be curved as shown at 31 to assure that the loop material will conform compactly within the body of adapter 18.

Fig. 2 shows the loop 24 and adapter 18 assembled, the adapter being threadably secured to the innermost spring by engagement of the helical recess 19 with the inner helical surface of spring 12. The helical recess 19 is preferably formed at a pitch substantially equal to the coil spacing of the spring when said spring is under initial preload. After this assembly is completed, adapter 16 shown in readiness for assembly with spring 11 is threaded over the loop 24 by virtue of a cylindrical bore 32 provided therein and is threadably engaged with the inner surface of the outer spring 11. The spacing of the helical recess 17 formed on the outer surface of adapter 16 likewise positions the coils of spring 11 a distance comparable to that assumed :by the entire spring when said spring is under initial preload.

In the unstressed, assembled condition illustrated in Fig. l the faces 33 and 34 of adapters 16 and 18 respectively preferably, but not necessarily, contact each other. If so assembled, when the spring pack is subjected to an initial tensional load, all springs will be stressed simultaneously. However, where a gradually increasing spring force function is .a desirable feature, a calculated gap may exist between faces 33 and 34 determined by the relative spring lengths to permit the first or innermost spring to be stressed initially until said spring has extended a distance equal to said gap, at which time the force of said first spring is supplemented by that of the second spring, and so on, for as many such springs as are contained in the spring pack. 5

Only one end of a spring pack is illustrated and described to enable an understanding of construction of the anchor means. Identical anchor means may be employed at the opposite end of the pack.

We claim:

An anchor assembly for a pair of concentric coil springs used under tension which comprises a first plug having an external helical groove to receive end coils of the inner spring, said first plug having axially extending diametrically opposed grooves throughout its length, an elongated loop embracing the first plug with parts disposed in said axially extending grooves and underlying the coils of said inner spring on the first plug, and a second plug with a helical groove to receive the end coils of the outer spring and a central :bore of a diameter sufliciently large to embrace said loop, one end of the second plug abutting one end of the first plug in assembly, and the loop extending through the bore and beyond the opposite end of the second plug.

References Cited in the file of this patent UNITED STATES PATENTS 571,972 Ianney Nov. 24, 1896 575,451 Yost Ian. 19, 1897 1,040,195 Harsh Oct. 1, 1912 2,248,447 Wood July 8, 1941 2,593,940 Van Meter Apr. 22, 1952 

